The invention relates generally to a medical instrument cannula.
A cannula is a thin surgical tube inserted into a body cavity or duct through which various medical instruments (e.g. endoscopes, trocars, suture forceps) access the body cavity or duct. Because the same cannula is used to introduce different medical instruments to a particular surgical location (e.g. at different stages of a procedure) damage is minimized to the surrounding tissue. As a result, an increasing number of medical instruments are being developed for use with a cannula.
In certain surgical procedures, it is desirable to fix the medical instrument to the cannula to prevent the instrument from shifting. Many medical instruments, therefore, are designed to releasably interface with a complementary cannula. In one type of interface, the medical instrument includes an engaging portion in the form of a hub having radially extending tabs which are received within a complementary groove or recess formed at the proximal end of the cannula. This arrangement is often referred to as a xe2x80x9cStorz-typexe2x80x9d interface. However, there is no single, standard releasable interface, even for instruments having a Storz-type interface. Instead, manufacturers of medical instruments have adapted their own, sometimes similar, versions of interfaces for coupling their own medical instruments to a complementary cannula.
However, the dimensions of the hubs of the medical instruments and the geometries of the grooves of the cannulas are sufficiently different to generally prevent using a medical instrument made by one manufacturer with a cannula made by another manufacturer. This can be problematic when a surgeon desires using medical instruments from different manufacturers during the same surgical procedure. In some cases, the coupling designs of the different manufacturers are sufficiently similar that a surgeon may, unsuccessfully, attempt to use non-compatible instruments and cannulas together, which can cause frustration and delay.
The invention relates to a coupling interface for a cannula adapted to receive and engage a wide variety of medical instruments having engaging portions which are different.
In a general aspect of the invention, the cannula includes an elongated insertion member having a passage for receiving the medical instrument and a clamping assembly disposed at the proximal end of the elongated insertion member to engage the medical instrument. The clamping assembly includes a second surface axially spaced from the first surface of the elongated insertion member, and a biasing member positioned to bias at least one of the first surface and the second surface axially toward each other and to clamp an engaging portion of the medical instrument between the first and second surfaces.
Another aspect of the invention relates the clamping assembly itself and described above. For example, the clamping assembly may be provided as a separate assembly which can be attached to any number of different cannulas.
The clamping assembly advantageously provides a variable space between the first surface and second surface for receiving a wide variety of medical instruments having differently shaped and sized engaging portions. Once the medical instrument is positioned so that its engaging portion is within the space, the biasing member maintains a force on at least one of the first and second surfaces ensuring that the instrument is well secured to the cannula.
Embodiments of the invention may include one or more of the following features.
The clamping assembly of the cannula further includes a user-manipulatable actuator for manipulating the clamping assembly to move at least one of the first and second surfaces toward and away from each other. The first surface and second surface are transverse to the axis of the elongated insertion member with the space between the first surface and second surface defining a channel for receiving the engaging portion of the medical instrument. The actuator includes an opening sized to receive the engaging portion of the medical instrument and is configured to be moved axially away from the elongated insertion section to allow the engaging portion of the medical instrument to be received within the channel. The actuator is then rotated about an axis of the elongated insertion member to engage the engaging portion within the channel in a closed position.
The opening is defined by a pair of opposing straight sides and a pair of opposing rounded sides, the opposing straight sides defining the second surface. The cannula includes an alignment post extending from the first surface of the elongated insertion member to align the engaging portion of the medical instrument to the clamping assembly.
The actuator includes a moveable member and the biasing member is positioned between the movable member and the elongated member. In one embodiment, the biasing member is a spring and is positioned between the moveable member and the first surface, such that axial movement of the actuator toward the second surface compresses the biasing member.
The cannula further includes a cover and a post for mechanically coupling the moveable member to the cover. The cover is removable to facilitate cleaning and replacement of the different parts of the clamping assembly.
The elongated insertion member has a guide slot for receiving the post and guiding the clamping assembly between the opened and the closed positions. The guide slot includes a first section extending axially along the insertion section to a second section which extends circumferentially around the insertion section, the second section extending to a third section extending axially along the insertion section, the post positioned within the first and third sections in the open and closed positions respectively. The passage of the elongated insertion member includes an O-ring seal. A torsion spring may be used to bias the clamping assembly to remain in a rotatably closed position.
In another aspect of the invention, a method of attaching a medical instrument to a cannula is provided. The cannula is of the type having an elongated insertion member having a proximal end with a first surface and a passage extending from the proximal end through a distal end of the insertion member. The method includes the following steps. The medical instrument is introduced through the passage. A clamping assembly is then used to engage an engaging portion of the medical instrument to the proximal end of the elongated insertion member. The clamping assembly includes a second surface axially spaced from the first surface of the elongated insertion member and a biasing member. The biasing member is positioned to bias at least one of the first surface and the second surface axially toward each other and to clamp the engaging portion of medical instrument between the first surface and the second surface.
Embodiments of this aspect of the invention may include one or more of the following features. The clamping assembly further includes the step of manipulating a user-manipulatable actuator to move at least one of the first and second surfaces of the clamping assembly toward and away from each other.
In one embodiment, the first surface and second surface are transverse to the axis of the elongated insertion member and the space between the first surface and second surface define a channel for receiving the engaging portion of the medical instrument. With this arrangement, the method further includes the following additional steps. The actuator is axially moved away from the elongated insertion section to allow the engaging portion of the medical instrument to be received within the channel. The actuator is then rotated about an axis of the elongated insertion member to engage the engaging portion within the channel in a closed position.
Other features and advantages of the invention will become apparent from the following description, drawings and from the claims.